GPT/GAM - how can I get dynamic key-values to appear in reports?

Question

I am setting targeting key-values via googletag. The final goal is to have such key-values in GAM reports.

This works with predefined key-values but it doesn't seem to work with dynamic key-values

On GAM I defined 2 keys:

• a predefined one called a_predefined_key
• a dynamic one called a_dynamic_key

key-values list

Client side I am setting both:

window.googletag.pubads().setTargeting('a_predefined_key', 'predefined_value_2');
window.googletag.pubads().setTargeting('a_dynamic_key', 'dynamic_value_1');

The 2 values appear in the cust_params:

https://securepubads.g.doubleclick.net/gampad/ads?...&cust_params=a_predefined_key%3Dpredefined_value_2%26a_dynamic_key%3Ddynamic_value_1...

The report settings look like this:

Report settings

The result of the report only shows the predefined key:

report

How do I get the dynamic key-values to appear in the report too?

Thank you in advance!